Research on the neural cell adhesion molecule (NCAM) has advanced the understanding of basic events in neural and skeletal muscle development. These studies provide evidence that NCAM is involved in several important processes including (a) the aggregation of cells during the formation of structures such as dorsal root ganglia, (b) the segregation of retinal cells into layers, and (c) the specification of nerve pathways and targets during innervation of the optic system and skeletal muscle. NCAM, which is detected in abundance in the developing heart, may also have an important role in the formation and innervation of cardiac tissue such as in (a) the aggregation of precardiac cells to form the heart tissue masses, (b) the formation of specialized layers of heart tissue, and (c) the specification of pathways and targets of innervation of the myocardium The role of NCAM will be investigated using the chicken embryo heart as a model. This system was chosen because it is well- characterized and readily accessible for manipulation both in vitro and in vivo. Three approaches will be pursued: (1) biochemical characterization of the cardiac NCAM; (2) detection of NCAM in histological sections during various stages of cardiogenesis; (3) observations of interacting embryonic heart cells in culture in the presence of specific antibodies and enzymes which perturb NCAM function. The fundamental goals of these studies are to aid in the understanding of both NCAM function and the multitude of dynamic cell and tissue interactions involved in normal cardiogenesis.